As America's power needs grow so does the need for transferring power from the source to the consumer. This is mainly accomplished by stringing high-tension wires from the power source through a maze of electrical suspension towers and telephone poles, to the consumer. The process of stringing high-tension wires is a difficult and dangerous one. First a lead rope must be strung from tower to tower which is followed by a heavy duty steel cable. These lines are drawn through a typical block to aid in the stringing process. Once the lead cable is in place and properly tensioned it must be transferred from the block used to draw it from tower to tower to a line stringing block which will eventually guide the conductor wires. This transfer of the lead cable from one block to another is time consuming and dangerous. It is much more efficient to draw the lead cable directly over the line stringing block, however in many instances this cannot be attempted because not all successive towers are in a linear configuration. This means that the stringing process often requires pulling from an angle. This procedure has a tendency to cause the lead cable to jump out of the groove in the pulley sheave of the stringing block. In order to prevent this unfortunate and time consuming event the instant invention attaches directly to a line stringing block and guides the lead cable preventing it from jumping off the block during an angle pull. This allows the line stringing block to be used in the first instance, thus eliminating the need for transferring the lead cable from one block to another. The inherent efficiency of this process as compared to the other combined with the added safety factors, betokens a strong felt yet unfulfilled need for the attachment according to the instant application.
Once the lead cable is strung it serves as a tag line for the conductor wire or wires. Tension is still maintained so that the conductor wires do not carry slack which will cause them to come in contact with the ground. The conductor wires must be handled with care to prevent any damage. The conductor wires are attached to a running board at the end of the lead cable. The roller guides in the instant invention are allowed to contact the lead cable as it is being strung, however the rollers must be retracted when the conductor wires approach to insure that no damage is incurred to the conductor wires. The instant invention is retractable so that the rollers can be withdrawn from the engaging position by releasing a pin which allows the rollers to swing out of the way to a ready position. Thus the entire stringing process is made more efficient by the elimination of unnecessary steps.
The following U.S. patents reflect the state of the art of which applicant is aware, in so far as these references appear germane to the patent process: Nos.
2,879,031: Livingston PA1 3,077,337: Cronkright PA1 3,145,973: MacFarlane PA1 3,584,837: Reilly PA1 3,720,399: Bozeman PA1 4,039,141: Lindsey
Of these references, the patent to MacFarlane is closest to the instant invention, because he teaches the use of a line stringing block that includes a lead cable guide means for line stringing blocks, which will guide the running board into the stringing block in proper alignment for passing therethrough and which will automatically spring out of the path of the running board as it enters the stringing block. MacFarlane teaches the use of rollers contained on shafts affixed to brackets arranged in opposed overlapping relationship.
The instant invention distinguishes thereover in that it pivots from a first to a second position when actuated manually. This allows the operator to determine the most advantageous moment to disengage the roller guides from the lead cable. The instant invention is further distinguished in that it may be applied in alternate embodiments to a single strand stringing block or a multiple strand stringing block.
MacFarlane teaches the use of four rollers through which the lead cable must be threaded. The instant invention accomplishes a similar task with but two rollers requiring no threading of the lead cable. The release of the rollers in MacFarlane requires the impact of the running board on the rollers to push them forward before they rotate to a neutral position. Therefore any forward force on the MacFarlane rollers can release them prematurely. The lead cable often carries tensions exceeding 5,000 lbs and it must often be drawn through the stringing block at an angle. This causes the stringing block to agitate and rotate as much as 90.degree. from its original, unloaded, hanging position and puts a great deal of strain on the rollers. During an angle pull a forward force is applied to the rollers which in the case of MacFarlane would trip the releasing mechanism for the rollers at an inappropriate time. This problem is overcome in the instant invention because the rollers are locked in position until the operator decides to release them.
Furthermore, the direction in which the lead cable tends to migrate on the stringing block is predetermined by the angle from which the lead cable is pulled. Also, the maximum angle at which the lead cable can be pulled through the stringing block is set forth in the specifications provided by the wire manufacturers or the power company. If the angle is to severe, then a pair of stringing blocks are used in tandem in conjunction with a spreader bar. Since the stringing angle is known beforehand by the alignment of the suspension towers and the specifications, only one pair of guide rollers need be applied to the appropriate side of the stringing block. The instant invention mounts easily to either side of the stringing block, thus adapting for any angle pull.
The other references further define the state of the art.